Various robotic laser systems have been developed and have been utilized in various applications, such as in automotive production systems. These robotic laser systems typically combine a laser system with an existent or an improved robot system, thus reducing development costs.
UK Patent No. 2,134,071 describes a rotating and translating optical joint comprising a mirror for directing a collimated laser beam through a robot. An apparatus for moving the joint is also disclosed, as is a robot built from a plurality of such joints.
A combination of two of the joints described in UK Patent No. 2,134,071 which rotate with respect to each other is known as a rotary elbow and is typically placed at every rotary joint of the robot. It is known in the art that the two mirrors of such a rotary elbow must be maintained very accurately parallel in three dimensions. Any misalignment has a potential for causing large deviations of the laser beam. If a misaligned rotary elbow is located roughly 2.5 meters from the end of the optical path, a laser beam impinging upon it will be deflected by as much as a few millimeters. This deflection reduces the accuracy with which the laser beam can be aimed.
There is known a COBRA robotic laser which is built by Ferranti Laser Systems of the UK and which comprises a Ferranti Laser System laser system and an ASEA articular robot. The laser beam of the Cobra is split before entering the robot and the two resultant beams are directed along the two sides of the ASEA robot. Two rotary elbows, one on each side of the robot, are placed at each of the six joints and thus, the system comprises 24 mirrors, the entirety of which must be accurately aligned in three dimensions in order to avoid unacceptable divergence of the laser beam.
U.S. Pat. No. 4,698,483 discloses another robotic laser system, a combination of the "SMART" Robot by Comau of Italy with a laser system. This five degree of freedom system utilizes nine mirrors to bring the laser beam to the cutting location. Although the number of mirrors utilized is reduced over the prior art, inaccuracies as described above, resulting from the difficulties involved in aligning nine mirrors, remain.
Yet another robotic laser system, the L-100 manufactured by General Motors Fanuc (GMF) of the U.S., is known in the art. Similar to the other companies described hereinabove, GMF incorporates a laser system into an existing robot, however, the robot chosen has simple mechanics and requires only four mirrors. The robotic system is designed such that the laser beam enters the robot vertically from above and impinges upon a rotary elbow early in the optical path. If it is desired to combine two robots, it is known in the art to add a beam director, which typically comprises two mirrors each pointing towards one of the two robots and which directs the beam horizontally, and one mirror per robot to direct the beam to enter the robot vertically.
The reduced number of mirrors on the L-100 enhances its ability to produce a laser beam with little divergence and with fairly small deviations; however, the existing robot is not designed for the accuracies required by the optical path. The robot has production tolerances on its mechanical parts that, as they accumulate, become too high to ensure an accurate optical path. Moreover, the rotary elbow at the beginning of the optical path can cause divergence of the laser beam.